c. 1600, in reference to the practice of punishing mutinous military units by capital execution of one in every 10, by lot; from Latin decimatus, past participle of decimare "the removal or destruction of one-tenth," from decem "ten" (from PIE root *dekm- "ten"). The killing of one in ten, chosen by lots, from a rebellious city or a mutinous army was a common punishment in classical times. The word has been used (incorrectly, to the irritation of pedants) since 1660s for "destroy a large portion of." Related: Decimated; decimating.